Maybe I Signed Up for Karaoke Instead of Spin by Accident?

It takes a lot to take the air out of my sails, but an unimpressive spin class will do that to me right quick. I actually felt bad that I’d made a friend come with me to this class because it was a pretty uninspiring way to spend 45 minutes. I have a limited amount of time to dedicate to my fitness regime: I don’t have time to ef around like this…

This is a mash up of “take the wind out of my sails” (feel less confident) and “let the air out of my tires” (make someone depressed). I think he meant the latter. See also a previous malaphor – “he took the thunder out of my sails”.